Vicious (adjective)

1. Having or showing a desire to harm or kill others.
2. Characterized by cruelty or brutality.
3. Mean-spirited or spiteful.
4. Bad or harmful in a way that is not easily controlled or corrected.

Origin:

Late middle english: from old french vicieux, from latin vitiosus "full of faults", from vitium "fault, vice".

Examples:

1. The dog was vicious and bit several people.
2. The criminal had a vicious streak.
3. The attack was vicious and unprovoked.
4. The critique was vicious and personal.
5. The storm was vicious and caused extensive damage.